An organic electroluminescent device is a device wherein a luminous layer containing a luminescent material is sandwiched between a hole transport layer and an electron transport layer, and an anode and a cathode are further provided on the outside, so as to utilize emission of light (fluorescence or phosphorescence) at the time of deactivation of excitons formed by recombination of holes and electrons injected into the luminous layer, and it is applied not only to small size displays but also to large-screen televisions and lighting, etc. Here, the hole transport layer may sometimes be constituted as divided into a hole transport layer and a hole injection layer; the luminous layer may sometimes be constituted as divided into an electron blocking layer, a luminous layer and a hole blocking layer; and the electron transport layer may sometimes be constituted as divided into an electron transport layer and an electron injection layer. Further, there may be a case where as a carrier transport layer (an electron transport layer or a hole transport layer) in an organic electroluminescent device, a metal, an organic metal compound or a co-deposited film doped with an organic compound, is used.
Conventional organic electroluminescent devices were not put into practical use, since their drive voltage was high, their emission luminance or luminous efficiency was low, and their service life was remarkably low, as compared to inorganic light emitting diodes. Although recent organic EL devices have been gradually improved, with respect to luminous efficiency characteristics, drive voltage characteristic, long service life characteristics, further excellent material is required. Further, depending upon applications such as automotive applications, etc., high thermal resistance may sometimes be required, and the material is required to have a high glass transition temperature (Tg).
As electron transport materials excellent in long service life for organic electroluminescent devices, cyclic azine compounds disclosed in Patent Document 1 or 2 may be mentioned. However, with respect to the thermal resistance of the materials, as well as with respect to the service life and luminous efficiency of the organic electroluminescent devices, further improvement has been desired.